1. Field of the Invention
The present invention relates to a fixing device (tool-less blade clamp) for fixing a rotary blade such as a saw blade to a spindle without the use of a special tool in a rotary tool such as, for example, a portable circular saw.
2. Description of the Related Art
Conventionally, as a technique relating to this kind of fixing devices, for example, a tool-less blade clamp assembly (fixing screw) which can be manually loosened without using a tool by utilizing a ratchet mechanism in order to prevent over-tightening is described in U.S. Pat. No. 6,843,627.
In addition, in Japanese Laid-Open Patent Publication No. 2001-520734, a retractable lever is provided in a fixing nut tightened to a threaded shaft part of a spindle, and the fixing nut can be tightened to the threaded shaft part of the spindle with a large torque while this lever is grasped, thereby enabling a user to firmly fix a rotary blade to the spindle without using a special tool such as a spanner, etc. After the tightening has been completed, the lever is retracted not to extend from the fixing nut so as not to interfere with the rotational movement of the rotary blade. Further, also in the case that the fixing nut is loosened, it is possible to pull out this lever and rotate the fixing unit in the loosening direction with a large torque, so that a user can manually loosen the fixing nut and remove the rotary blade without using a special tool.
However, though a fixing screw described in U.S. Pat. No. 6,843,627 is characterized document does not disclose a technique for tightening it firmly.
Further, the technique described in Japanese Laid-Open Patent Publication No. 2001-520734 provides a fixing nut for fixing a saw blade to a spindle of a cutting machine body. Though this fixing nut can be tightened and loosened with a large torque, Japanese Laid-Open Patent Publication No. 2001-520734 does not disclose a technique for its compactification with respect to a radial direction or a thickness direction.
Therefore, there is a need in the art for a fixing device for manual rotational operation of a user, which can be tightened or loosened with a large torque and is compactified with respect to its radial direction or thickness direction to enable an adequate cutting depth when performing a so-called oblique cutting operation in a portable circular saw.